Circuit Description
The camshaft position (CMP) sensor has a 12-volt reference circuit, a low reference circuit, and a signal circuit. The powertrain control module (PCM) supplies 12 volts to the sensor. The PCM determines which pair of cylinders is at top dead center (TDC) using the crankshaft position (CKP) sensor data. The CMP sensor signal, when combined with the CKP sensor signal, enables the PCM to determine exactly which cylinder is on a firing stroke. The PCM can then properly synchronize the ignition system, fuel injectors, and knock control.
Conditions for Running the DTC
The engine is cranking or running
Conditions for Setting the DTC
The PCM detects a problem with the CMP sensor signal.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
Ensure that the engine grounds are clean and tight, including the main battery ground cable at the engine block.
If no trouble is found with the CMP sensor or the related circuitry, and DTC P0340 continues to set, the engine should be checked for incorrect cam timing.
CKP/CMP sensor DTCs may set if the key is turned to Start and the starter is inoperative. If P0335, P0340, and P0385 are set and no trouble is found, check for the following:
| • | Is there a no-crank condition or an intermittent no-crank condition? |
| • | Was an attempt made to crank the engine with the shift lever not in P/N? |
DTC P0340 may set if engine cranking speed is below 120 RPM. Review Freeze Frame/Failure Records to determine if the DTC set during cranking with an engine speed of less than 120 RPM. If this was the case, correct the cause of the slow cranking speed. The scan tool parameter CMP Sensor Data will not display an accurate RPM value below 120 RPM.
If the problem is intermittent, refer to Intermittent Conditions .
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the scan tool indicate a CMP sensor RPM and a CAM signal are present? | -- | Go to Step 3 | Go to Step 5 | |
3 |
Does the DTC reset? | -- | Go to Step 5 | Go to Step 4 |
4 | Move the related harnesses and connectors by hand while monitoring the scan tool display. Does the CAM signal display change to No or does the RPM become erratic? | -- | Go to Step 11 | Go to Diagnostic Aids |
5 |
Does the voltage equal the specified value? | B+ | Go to Step 6 | Go to Step 12 |
6 | Connect the DMM between the 12-volt reference circuit and the low reference circuit in the CMP sensor harness connector. Does the voltage equal the specified value? | B+ | Go to Step 7 | Go to Step 13 |
7 |
Is RPM indicated on the scan tool? | -- | Go to Step 17 | Go to Step 8 |
8 |
Is voltage present? | -- | Go to Step 16 | Go to Step 9 |
9 | Use the DMM in order to inspect the signal circuit for continuity between the CMP sensor harness connector and the PCM harness connector. Is the resistance less than or equal to the specified value? | 5 ohms | Go to Step 10 | Go to Step 14 |
10 | Use the DMM in order to inspect for continuity between the signal circuit and ground. The DMM should display infinite resistance. Is the resistance infinite? | ∞ | Go to Step 19 | Go to Step 15 |
11 | Repair the harness and the connections as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
12 | Repair the sensor 12-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | Go to Step 19 |
13 | Repair the open or the high resistance in the sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | Go to Step 19 |
14 | Repair the open or the high resistance in the sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
15 | Repair the short to ground in the sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
16 | Repair the short to power in the sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- |
17 | Inspect for poor connections and poor terminal tension at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 18 |
18 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the repair? | -- | Go to Step 21 | -- |
19 | Inspect for poor connections and poor terminal tension at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
20 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 21 | -- |
21 |
Does the DTC run and pass? | -- | Go to Step 22 | Go to Step 2 |
22 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
